Flame-retardant hollow fiber with silicone-free soft-touch finish

ABSTRACT

The invention relates to a flame-retardant, modified hollow fiber with a silicone-free soft-touch finish feature, and also to a method for production thereof and the use thereof for fiberfill fiber products, in particular in the fiber filling of clothing, cushions, furniture, insulation, quilts, filters, upholstery (e.g., automobiles), sleeping bags, mattress covers and mattresses. In general, the hollow fibers used for these applications are those with flame-retardant, phosphorus-containing compounds. Polyester hollow fibers are used preferably as hollow fibers.

The invention relates to a flame-retardant modified hollow fiber with a silicone-free soft-touch finish, and to a method for the production thereof and to the use thereof for fiber-filled products.

Fiber fillings can be used in many applications, for example for clothes, cushions, furniture, insulation, quilts, filters, upholstery (e.g. in automobiles), sleeping bags, mattress covers and mattresses. In general, the hollow fibers used for these applications are hollow fibers which are made flame-retardant by means of phosphorus-containing compounds. The hollow fibers used are preferably polyester hollow fibers.

The production of such flame-retardant modified polyester fibers, in which the polyester has phosphorus-containing chain links co-condensed therewith, is known per se. Reference is made at this point to the German patent applications and patent specifications DE 22 36 037, DE 22 42 002, DE 23 28 00 343, DE 23 46 787, DE 24 54 189.

The fibers described therein have to date been used as such only for the purpose of flame retardancy.

Furthermore, fiber fillings are given a pleasant feel, improved fluffiness, improved surface smoothness and improved resiliency by means of a so-called soft-touch finish. For this soft-touch finish, a silicone-based softener is used according to the prior art, as disclosed for example in WO 2004/007 347 (Trevira GmbH), U.S. Pat. No. 3,271,189 (Hofmann) and in U.S. Pat. No. 3,454,422 (Mead et al.).

However, for such fibers with a silicone-containing soft-touch finish, it is known that the flame-retardant properties are very significantly impaired by this silicone-containing soft-touch finish.

The object of the present invention is therefore to equip flame-retardant hollow fibers with a soft-touch finish which does not impair the flame-retardant properties of the hollow fibers.

It has been found that, in the case of flame-retardant polyester hollow fibers which are provided with the silicone-free soft-touch finish according to the invention, on the one hand the flame-retardant properties of the hollow fibers are not impaired by the applied soft-touch finish and on the other hand the desired soft touch is retained.

The present invention therefore relates to flame-retardant modified fibers based on melt-spinnable polymers, in particular based on polyesters, characterized in that these fibers are provided with a soft-touch finish which is silicone-free.

The fibers according to the invention made from melt-spinnable polymers are preferably fibers based on polyesters. The polyester material in question may in principle be any known type suitable for fiber production. Such polyesters consist mainly of building blocks derived from aromatic dicarboxylic acids and from aliphatic diols. Customary aromatic dicarboxylic acid building blocks are the divalent residues of benzenedicarboxylic acids, in particular of terephthalic acid and of isophthalic acid. Customary diols contain 2 to 4 carbon atoms, ethylene glycol being particularly suitable. Fibers which consist of polyethylene terephthalate in a proportion of at least 85 mol % are particularly advantageous. The remaining 15 mol % consists of dicarboxylic acid units and glycol units which act as so-called modifiers and which make it possible for the person skilled in the art to influence in a targeted manner the physical and chemical properties of the filaments produced. Examples of such dicarboxylic acid units are residues of isophthalic acid or of aliphatic dicarboxylic acids, such as glutaric acid, adipic acid and sebacic acid. Examples of diol residues acting as modifiers are those of longer-chain diols, e.g. of propanediol or butanediol, of di- or triethylene glycol, or, if present in small quantity, of polyglycol having a molecular weight of approx. 500 to 2000.

Particular preference is given to polyesters which contain at least 95 mol % polyethylene terephthalate (PET), in particular PET that is not modified with dicarboxylic acid units and/or glycol units.

The flame-retardant modification of the polyester fibers is achieved by using flame-retardant modified polyesters. Such flame-retardant modified polyesters are known. They contain additions of halogen compounds, in particular bromine compounds, or, in a particularly advantageous manner, they contain phosphorus compounds which are incorporated in the polyester chain by condensation.

In the context of the invention, these phosphorus-containing chain links incorporated by condensation are to be understood as chain links which are arranged in the linear chain of the polymer molecule (longest chain) but also in any side chains and branches that may be present.

Particular preference is given to flame-retardant modified polyesters which contain components of formula (I)

which are incorporated in the chain by condensation and in which R is alkylene or polymethylene containing 2 to 6 carbon atoms or phenyl and R¹ is alkyl containing 1 to 6 carbon atoms, aryl or aralkyl. In formula (I), preferably R is ethylene and R¹ is methyl, ethyl, phenyl or o-, m- or p-methylphenyl, in particular methyl. Such polyesters are described for example in DE-A-39 40 713. The polyesters used according to the invention preferably have a molecular weight corresponding to an intrinsic viscosity (IV), measured in a solution of 1 g of polymer in 100 ml of dichloroacetic acid at 25° C., of 0.45 to 0.85.

The silicone-free soft-touch finish according to the invention is a mixture comprising at least one polyether and at least one fatty acid condensation product. According to the invention, this mixture preferably has a mixing ratio (weight) of polyether:fatty acid condensation product of 10:1 to 1:1, in particular 5:1 to 2:1, particularly preferably 4:1.

Polyethers suitable for the soft-touch finish according to the invention are compounds having the general formula

in which the radicals R³, R⁴ may be identical or different and are selected from hydrogen, straight-chain and/or branched alkyl and/or alkenyl groups, and aromatic and/or heteroaromatic groups, R² may be identical or different and are selected from straight-chain and/or branched alkyl and/or alkenyl groups, and aromatic and/or heteroaromatic groups, and n is a number equal to at least 1, preferably at least 2.

Preferred radicals R² are straight-chain or branched alkyl groups, in particular ethyl groups (polyethylene glycol) or propyl groups (propylene glycol). The end groups R³, R⁴ are usually hydrogen but may also be substituted with the same groups as mentioned above for R³, R⁴.

Preferred compounds of formula (II) are nonionogenic polyethers. It is also preferred if the polyethers are miscible with water and have as a 10% solution (percentage by weight) a pH value in the range from 6 to 9, in particular from 7 to 8, particularly preferably 7.5. It is also preferred if the dynamic viscosity of the polyethers (measured as a 10% solution in water) at 20° C. (HTC51) is preferably between 50 and 80 mPas, in particular between 60 and 70 mPas, particularly preferably 65 mPas.

Such polyethers are commercially available, for example under the trade name Duron®FF 1751, a product from the company CHT R. Beitlich GmbH.

Fatty acid condensation products according to the invention which are suitable for the soft-touch finish are compounds of fatty acids having the general formula

R⁵—COOH,

in which R⁵ represents straight-chain or branched alkyl or alkenyl groups containing 6 to 30 carbon atoms, preferably 6 to 26 carbon atoms, with aliphatic or aromatic, monofunctional or polyfunctional alcohols or amines.

Among these fatty acid condensation products mentioned above, preference is given according to the invention to fatty acid condensation products, in particular cationic fatty acid condensation products, which are fully miscible with water and which have as a 10% solution (percentage by weight) a pH value in the range from 1 to 6, preferably 2 to 5, particularly preferably 3 to 4. The dynamic viscosity thereof (measured as a 10% by weight solution in water) at 20° C. is preferably between 80 and 120 mPas, more preferably between 90 and 110 mPas, particularly preferably around 100 mPas.

One such commercially available fatty acid condensation product is Duron® FF 1995, a product from the company CHT R. Beitlich GmbH.

Particular preference is given to a soft-touch finish comprising (i) nonionogenic polyethers, the pH value of which (measured as a 10% by weight solution in water at 20° C.) is between 7 and 8 and the dynamic viscosity of which (measured as a 10% by weight solution in water at 20° C.) is between 50 and 80 mPas, and (ii) cationic fatty acid condensation products, the pH value of which (measured as a 10% by weight solution in water at 20° C.) is in the range from 2 to 5 and the dynamic viscosity of which (measured as a 10% by weight solution in water) at 20° C. is between 80 and 120 mPas, and wherein the mixing ratio (parts by weight) of nonionogenic polyether (i) to cationic fatty acid condensation product (ii) is 5:1 to 2:1.

With very particular preference, the abovementioned mixture of (i) nonionogenic polyether and (ii) cationic fatty acid condensation product is a mixture in which the polyethers (i) comprise various polyethers selected from the group consisting of polyethylene glycol, polypropylene glycol or mixtures of polyethylene glycol and polypropylene glycol.

With the use according to the invention of this silicone-free soft-touch finish on the flame-retardant fibers, it is possible to produce fiber products, in particular for the fiber-filled sector, which have both a soft touch and flame-retardant properties.

Silicone-free is understood here to mean that so little silicone-containing material is contained therein that the flame-retardant properties according to the invention are not impaired. This is the case for quantities of at most around 10 ppm of silicone-containing material relative to the finished hollow fiber, preferably less than around 1 ppm, particularly preferably less than around 0.1 ppm.

The fibers may have round, oval and other suitable cross-sections or also other shapes, such as for example dumbbell-shaped, kidney-shaped, triangular or trilobal or multilobal cross-sections. Preferably, hollow fibers are used.

In general, polyester fibers have titers in the range from 0.9 to 16 dtex. Use is preferably made of polyester hollow fibers having the aforementioned values, preferably having titers from 0.9 to 17 dtex, particularly preferably 4 to 13 dtex. If the polyester hollow fibers according to the invention are to be used as staple fibers, they have a cut length (staple length) of 1 to 150 mm, preferably 8 to 100 mm and particularly preferably 24 to 80 mm.

In particular embodiments of the invention, the polyester fibers consist of a titer mixture and/or a mixture of fibers of different staple length.

If the polyester fibers according to the invention are to be used for textile applications or as fiber-filled packing, a texturing is advantageous, particularly a crimping.

According to the invention, the degree of crimping is 2 crimps (bends) per cm (Bg) or more, preferably 3 bends per cm or more.

The number of bends per cm must moreover be in a certain ratio to the so-called crimping K1. K1 preferably has values of at least 15%, preferably at least 18%. Accordingly, for a number of bends per cm Bg of 3.0, the ratio of crimping to the number of bends per cm preferably lies in the range from 5≦K1/Bg≦6.

In the context of the invention, crimping is understood by the following ratio:

${K\; 1} = \frac{{Lv} - {Lk}}{Lv}$

in which L_(k) is the length of the crimped staple fiber in the relaxed, released state and L_(v) is the length of the same fiber but in the stretched state, i.e. the fiber is then practically rectilinear without any bends. The stretching takes place under the application of the so-called decrimping force. This is determined in preliminary tests by means of a tangent applied to the force/extension diagram for the respective fiber.

The flame-retardant fibers according to the invention may additionally contain further additives which are usually used in the prior art. These are understood to mean in particular antioxidants, stabilizers (e.g. UV stabilizers), matting agents (e.g. TiO₂, zinc sulfide or zinc oxide), pigments (e.g. TiO₂), additional flame retardants, antistatic agents, dyes, fillers (e.g. calcium carbonate), antimicrobial agents, bioactive agents, optical brighteners, extenders and further processing aids.

Such additives may be added to the polymer at any point in time during the polymer production or can be applied to the fibers together with the softener.

The fibers are produced as follows: polymers are spun to form filaments, optionally with the use of lubricants, and then are processed to form fibers, the fibers are stretched and crimped, and optionally an antistatic agent is applied to the fibers. In the case of producing staple fibers, the fibers are cut and then pressed as so-called flocks into bales and packed.

The production of the fibers takes place using conventional methods and systems, such as those preferred in the technical field in connection with polyester fibers. By way of example, numerous spinning methods are described in U.S. Pat. No. 3,816,486, U.S. Pat. No. 4,639,347, GB 1 254 826 and JP 11-189938.

The spinning rate is preferably 800 meters per minute or more and is typically 1600 meters per minute or less. The spinning temperature is typically 255° C. or more and 305° C. or less. With particular preference, the spinning is carried out at around 280° C.

The spinnerette is a conventional spinnerette of the type used for conventional polyesters, the hole size, arrangement and number being dependent on the desired fibers and the spinning system.

The quenching of the polyester filaments thus spun from the melt can be carried out in a conventional manner by using air or other fluids as described in the technical field (e.g. nitrogen). Transverse flow, radial, asymmetric or other cooling methods may be used. Air is preferably blown on for quenching purposes.

After the cooling, conventional spin finishes can be applied by means of standard methods.

For further processing, the fiber filaments thus produced are initially deposited in cans.

According to one preferred method, the melt-spun fiber filaments are picked up onto a tow cylinder and then a plurality of tow cylinders are brought together and a large tow is generated from the fiber filaments. Thereafter, the fiber tow can be stretched using conventional methods, preferably at 10 to 110 m/min. The stretching ratios preferably reach 1.25 to 4, more preferably 2.5 to 3.5 and particularly preferably 3.2. The temperature during the stretching lies in the range of the glass transition temperature of the polyester tow to be stretched and is preferably 40° C. to 80° C. and particularly preferably 69° C. The post-treatment is carried out at approx. 150° to 165° C. in order to ensure good drying. The stretching may optionally be carried out using a two-stage stretching process (in this regard, see for example U.S. Pat. No. 3,816,486). Before and during the stretching, one or more surface finishes may be applied using conventional methods.

Preferably, the silicone-free soft-touch finish according to the invention is applied between the stretching and the crimping. The application takes place using conventional techniques, in particular by spraying or by means of an application roller. The applied quantity is between 0.4 and 0.5% of the fiber weight and is preferably 0.46%.

For the crimping of the fibers thus stretched, use may be made of conventional methods of mechanical crimping using crimping machines known per se. Preference is given to a steam-assisted mechanical device for crimping staple fibers, such as for example a stuffer box. However, use may also be made of fibers crimped by other methods, such as e.g. also three-dimensionally crimped fibers. In order to carry out the crimping, the tow is firstly heated to a temperature in the range from 60° to 100° C., preferably 70° to 85° C., particularly preferably to around 83° C. and is treated at a pressure of the tow inlet rollers of 1.0 to 2.0 bar, particularly preferably around 1.5 bar, a pressure in the crimping box of 0.5 to 1.0 bar, particularly preferably 0.8 bar, with steam at between 1.0 and 2.0 kg/min, particularly preferably 1.5 kg/min.

A further surface finish may be applied in the crimping device using conventional methods.

The fibers are relaxed and/or fixed at 150° to 165° C. in the oven. The preparation requires no dedicated fixing step.

An antistatic finish may optionally be applied to the fibers after the relaxing of the latter.

If desired, the fibers may also be provided with a low-pill finish.

In order to produce staple fibers, the textured fibers are picked up and then this is followed by cutting and optionally hardening and storing in pressed bales as flock. The staple fibers of the present invention are preferably cut on a mechanical cutting device downstream of the relaxation step. In order to produce types of tow, the cutting may be omitted. These types of tow are stored in bales in uncut form and compressed.

Another subject matter is the use of the fiber products according to the invention as fiber fillings or in textile fabrics.

The use of the fiber products according to the invention as fiber fillings includes fillings for filled coverings, such as e.g. pillows, duvets, quilts and the like, as well as for mattresses and sleeping bags, insulating material and upholstery, for example for furniture and in the automobile sector, as well as filters.

Textile fabrics according to the invention are for example clothes, the top and bottom covers of the products mentioned above, as well as mattress covers.

EXAMPLE

The invention will be explained in more detail on the basis of the following example:

A staple fiber having a hollow profile is spun from the melt in the manner customary for fibers made from the flame-retardant raw material, is cooled by blowing with air, is provided with a customary staple fiber preparation and is deposited in cans for processing on the conveyor line.

The spun goods are collected together as a fiber tow over an inlet rake and are drawn in by a first septet, consisting of seven rotating rollers, and passed through an immersion bath, where they are temperature-controlled and once again provided with preparation. The spun goods are transported onward by a further septet. The stretching takes place on the 6th or 7th roller of this septet, or between said septet and a further septet running at a speed that is greater by the factor of the stretching. Thereafter, the fiber is crimped in a stuffer box, fixed or dried in an oven and optionally cut. Between the stretching and the crimping, a silicone-free soft-touch finish is added by spraying or by means of an application roller.

The following textile-related values are determined on the fibers produced:

TABLE 1 Denier/dtex: 6.0 Tear strength/cN/tex: 40 Elongation at break /% 36 Heat shrinkage (200° C.)/%: 4 Crimping: Kl/%: 18 Bg/cm: 4 

1. A flame-retardant modified fiber based on melt-spinnable polyester, characterized in that the fiber is a polyester hollow fiber that is provided with a silicone-free soft-touch finish which comprises at least one polyether and at least one fatty acid condensation product.
 2. The flame-retardant modified fiber according to claim 1, characterized in that the soft-touch finish comprises at least one polyether and at least one fatty acid condensation product and the mixing ratio (weight) of polyether:fatty acid condensation product is 10:1 to 1:1.
 3. The flame-retardant modified fiber according to claim 1, characterized in that the polyether is one or more compounds having the general formula

in which the radicals R³, R⁴ may be identical or different and are selected from hydrogen, straight-chain and/or branched alkyl and/or alkenyl groups, and aromatic and/or heteroaromatic groups, R² may be identical or different and are selected from straight-chain and/or branched alkyl and/or alkenyl groups, and aromatic and/or heteroaromatic groups, and n is a number equal to at least
 1. 4. The flame-retardant modified fiber according to claim 3, characterized in that the polyether is polyethylene glycol and/or propylene glycol.
 5. The flame-retardant modified fiber according to claim 1, characterized in that the fatty acid condensation product is one or more condensation compounds of fatty acids having the general formula R⁵—COOH, in which R⁵ represents straight-chain or branched alkyl or alkenyl groups containing 6 to 30 carbon atoms, with aliphatic or aromatic, monofunctional or polyfunctional alcohols or amines.
 6. The flame-retardant modified fiber according to claim 1, characterized in that the fiber is a polyester staple fiber.
 7. The flame-retardant modified fiber according to claim 1, characterized in that the polyester fiber consists mainly of building blocks derived from aromatic dicarboxylic acids and from aliphatic diols.
 8. The flame-retardant modified fiber according to claim 7, characterized in that the aromatic dicarboxylic acids are divalent residues of benzenedicarboxylic acids.
 9. The flame-retardant modified fiber according to claim 8, characterized in that the fibers consist of polyethylene terephthalate in a proportion of at least 85 mol %.
 10. The flame-retardant modified fiber according to claim 7, characterized in that the aliphatic diols are those containing 2 to 4 carbon atoms.
 11. The flame-retardant modified fiber according to claim 1, characterized in that the flame retardancy based on the polyester is achieved by additions of halogen compounds or by phosphorus compounds which are incorporated in the polyester chain by condensation.
 12. The flame-retardant modified fiber according to claim 11, characterized in that the flame-retardant modified polyester contains components of formula (I)

which are incorporated in the chain by condensation and in which R is alkylene or polymethylene containing 2 to 6 carbon atoms or phenyl and R¹ is alkyl containing 1 to 6 carbon atoms, aryl or aralkyl.
 13. The flame-retardant modified fiber according to claim 12, characterized in that the components incorporated by condensation in the chain of the flame-retardant modified polyester may be arranged in the linear chain of the polymer molecule (longest chain) but also in any side chains and branches that may be present.
 14. The flame-retardant modified fiber according to claim 1, characterized in that the fiber is textured.
 15. The flame-retardant modified fiber according to claim 14, characterized in that the fiber is crimped.
 16. The flame-retardant modified fiber according to claim 15, characterized in that the crimping K1 is at least 15%.
 17. The flame-retardant modified fiber according to claim 1, characterized in that the fibers have titers in the range from 0.9 to 16 dtex, preferably 0.9 to 17 dtex.
 18. The flame-retardant modified fiber according to claim 1, characterized in that the fibers are in the form of staple fibers and have a staple length of 1 to 150 mm.
 19. A fiber fillings, containing the flame-retardant modified fibers according to claim
 1. 20. The filled coverings, filled with the fiber fillings according to claim
 19. 21. The filled coverings according to claim 20, wherein the filled coverings include pillows, duvets and quilts, mattresses, sleeping bags, insulating material, upholstery, and filters.
 22. A textile fabric, containing the flame-retardant modified fibers according to claim
 1. 23. The textile fabric according to claim 22, wherein the textile surfaces comprise the top and bottom covers of the filled coverings, and mattress covers. 